Colon surgery, or colectomy, involves removing a diseased or damaged section of the large intestine. The need for a colostomy bag depends on the nature and location of the procedure. Surgeons aim to reconnect the remaining healthy ends of the bowel, a procedure called an anastomosis. If reconnection is impossible or too risky, an ostomy—a surgically created opening called a stoma—is created to divert waste from the body. Whether this diversion is temporary or permanent depends on the underlying medical issue and the extent of tissue removal.
Types of Colon Surgery and Digestive Rerouting
Colon surgery encompasses several procedures. When a part of the colon is removed (resection), the surgeon typically aims to reconnect the remaining healthy bowel segments through an anastomosis. This reconnection is generally successful when the surgery involves the upper or right side of the colon, such as a right hemicolectomy.
The challenge of rejoining the bowel increases significantly as the surgery moves lower into the pelvis, involving the descending, sigmoid colon, or rectum. This area is anatomically constrained. Procedures like a low anterior resection place the anastomosis closer to the anus, increasing the risk of complications, such as leakage, due to decreased blood supply and increased bacterial load.
If the surgeon performs a proctocolectomy, removing the entire colon and rectum, a permanent ostomy is unavoidable. The lower the point of surgical removal, the more likely the surgeon will need to create a stoma to allow for proper healing or to serve as a new exit for waste.
Surgical Indications for an Ostomy
A surgeon may determine that creating an ostomy is the safer or only viable option for several medical and anatomical reasons. One common indication is emergency surgery for conditions like severe diverticulitis, trauma, or a perforated bowel, where the tissue is inflamed or infected. Attempting an immediate reconnection (anastomosis) in these cases is risky, as the compromised tissue is unlikely to heal properly.
Another indication is a procedure where the critical sphincter muscles that control bowel movements must be removed. For example, an Abdominoperineal Resection (APR) is required when cancer is located very low in the rectum or involves the anal sphincter. Since the natural mechanism for continence is removed in an APR, a permanent end colostomy is necessary to manage waste.
Even in planned surgeries where the rectum is preserved, a temporary ostomy may be created to protect a high-risk anastomosis. This diverts the fecal stream away from the newly joined bowel, allowing it time to heal without being stressed by passing stool. This measure significantly lowers the chance of an anastomotic leak, a severe complication that occurs when the surgical connection breaks down.
Temporary Diversion Versus Permanent Ostomy
The decision between a temporary and a permanent stoma is based on whether the downstream bowel can be safely restored to function. A temporary ostomy, often a loop colostomy or ileostomy, is created specifically to divert waste and allow a surgical site to rest and heal. This type of diversion is commonly used to protect a fresh anastomosis after a low anterior resection for rectal cancer.
Temporary ostomies are typically in place for a few weeks to six months, and once the healing is confirmed, a second surgery, called a reversal, is performed to reconnect the bowel. However, an ostomy becomes permanent when the lower part of the colon, the entire rectum, and the anal sphincter are removed, making the natural passage of stool impossible.
This permanent diversion is an end ostomy, where the remaining working end of the bowel is brought through the abdominal wall. Procedures like the Abdominoperineal Resection necessitate a permanent colostomy because the structures required for continence are completely removed. Therefore, the determining factor for permanence is the extent of the tissue removed and whether the anal mechanism remains intact.